There are numerous applications for controlling fluid flow, such as within a municipal water supply network or a private system for moving a water or chemical product, and it is sometimes advantageous to control fluid flow “in line” with piping used to transport that fluid from one location to another. While it can be desirable for fluid flow to be reversible in some applications, in various fluid systems it is desirable to allow the fluid to flow in only one direction at least some of the time or under certain conditions in various situations, and in other various situations is it desirable to allow fluid flow in only one direction at all times.
A check valve is a valve for allowing fluid flow in only one direction through the check valve. A check valve allows flow in only one direction by preventing flow reversal, i.e., flow in a direction opposite to the desired direction. Some check valves include a valve body having an inlet and an outlet and with a disc mounted within the valve body. The disc is positioned such that the disc covers the path from the outlet to the inlet during flow reversal, closing the valve, but moves away from the path when fluid flows from the inlet to the outlet, opening the valve. In a fluid piping system containing a pump and a check valve downstream of the pump, there is typically a time delay between when the pump stops pushing the fluid and when the check valve is fully closed. It is possible for flow reversal to occur if the valve does not close quickly enough. During flow reversal, the disc can slam closed quickly, creating noise and vibration in the piping system and potentially damaging the disc over long periods of use. “Valve slam” is another term used to describe the situation where the disc on a check valve, often as a result of flow reversal, is allowed to “slam” against the valve seat against which it is designed to seal.